Aqueous coating composition of acrylic polymer latex, acrylic polymer solution and aminoplast and method of making

ABSTRACT

Water-based paints having improved properties and application characteristics are disclosed. The paint, exclusive of optional components such as pigments, particulate fillers and catalysts, comprises a liquid, continuous aqueous phase. About 30 to about 50 percent by weight of this phase exclusive of the aforecited optional components, is made up of a mixture of (a) an amino resin crosslinking agent; (b) a mixture of at least two copolymers of acrylic monomers; and (c) an amine. The balance is water or, in certain embodiments, water and an organic solvent. The mixture of copolymers comprises (1) about 5 to about 50, preferably about 10 to about 30, parts by weight of a &#39;&#39;&#39;&#39;solution polymer,&#39;&#39;&#39;&#39; i.e., a carboxyfunctional copolymer of acrylic monomers that (i) is at least partially neutralized with an amine, (ii) is soluble in said aqueous phase, (iii) has average molecular weight (Mn) in the range of about 3,000 to about 20,000, and (iv) has Tg in the range of -15* to 50*C., and (2) about 50 to about 95, preferably about 70 to about 90, parts by weight of an &#39;&#39;&#39;&#39;emulsion polymer,&#39;&#39;&#39;&#39; i.e., a copolymer of acrylic monomers having carboxy, hydroxy or carboxy and hydroxy functionality that (i) is essentially insoluble in said continuous phase, (ii) has average molecular weight (Mn) in the range of about 3,000 to about 20,000, and (iii) has Tg of -15* to 50*C. The amino resin crosslinking agent is present in an amount in the range of about 15 to about 35 weight percent of the sum of the weight of solution polymer and the weight of emulsion polymer. The amine is a water-soluble amine and is present in an amount sufficient to solubilize the solution polymer in the aqueous phase at a pH range of about 7 to about 10, most commonly in the range of about 7.1 to about 8.5.

United States Patent 1191 Chang et al.

1 1 AQUEOUS COATING COMPOSITION OF ACRYLIC POLYMER LATEX, ACRYLIC POLYMER SOLUTION AND AMINOPLAST AND METHOD OF MAKING [751 Inventors: Yun-Feng Chang, Plymouth;

Mo-Fung Cheung, Warren; Santokh S. Labana, Dearborn Heights. all of Mich.

173] Assignee: Ford Motor Company, Dearborn.

Mich.

[221 Filed: June 3, I974 [211 Appl. No: 476,114

[521 U.S. CL... 260/29.4 UA; 160/8075; 260/808; 260/851; 260/856 [51] Int. C121 C08L 29/02; COSL 33/02;

C08L 61/24. COSL 61/28 [58] Field of Search 1. 260/294 UA. 851. 856

1561 References Cited UNITED STATES PATENTS 3.107.137 10/1963 Sven et al. r 260/856 3.218.280 11/1965 Koral et a1. 260/856 3.245.932 4/1966 Gla is et a1. 260/851 3.821.145 6/1974 Walus t 260/851 FOREIGN PATENTS OR APPLICATIONS 676.155 12/1963 Canada 260/294 UA Primary E.\'uminerMurray Tillman Assistant E.\aminer-Arthur H. Koeckert Attorney. Agem. or FirmO1in B. Johnson; Keith L. Zerschling 1571 ABSTRACT Watenbased paints having improved properties and 1 1 Nov. 11,1975

application characteristics are disclosed. The paint. exclusive of optional components such as pigments. particulate fillers and catalysts, comprises a liquid. continuous aqueous phase. About 30 to about 50 percent by weight of this phase exclusive of the aforecited optional components. is made up of a mixture of (a) an amino resin crosslinking agent; (b) a mixture of at least two copolymers of acrylic monomers; and (c) an amine. The balance is water or. in certain embodiments. water and an organic solvent. The mixture of copolymers comprises 1 J about to about 50. preferably about to about 30. parts by weight of a solution polymer." Le. a carboiyfunctional copolymer of acrylic monomers that (i) is at least partially neutralized with an amine. iii) is soluble in said aqueous phase. (iii! has average molecular weight (MN) in the range of about 3.000 to about 20,000. and (iv) has Tg in the range of to C. and (2) about 50 to about 95. preferably about to about 90. parts by weight of an emulsion polymer," ie. a copolymer of acrylic monomers ha ing carboxy, hydroxy or carboxy and hydroxy functionality that (i) is essentially insoluble in said continuous phase. (ii) has average molecular weight (M in the range of about 3,000 to about 20,000. and (iii) has Tg of l5 to 50C. The amino resin crosslinking agent is present in an amount in the range of about 15 to about 35 weight percent of the sum of the weight of solution polymer and the weight of emulsion polymer. The amine is a water-soluble amine and is present in an amount sufficient to solubilize the solution polymer in the aqueous phase at a pH range of about 7 to about 10. most commonly in the range of about 7.1 to about 8.5.

13 Claims, No Drawings AQUEOUS COATING COMPOSITION OF ACRYLIC POLYMER LATEX, ACRYLIC POLYMER SOLUTION AND AMINOPLAST AND METHOD OF MAKING BACKGROUND OF THE INVENTION Water-based paints of the prior art have included solution paints and emulsion (or latex) paints" with distinction being made with reference to the manner in which the sole or principal binder polymer is dispersed within the aqueous medium.

In those paints whereinthe sole or principal binder polymer is soluble in the aqueous medium, the polymer is ordinarily of low molecular weight. These paints can be formulated to provide coatings of very high gloss. They tend to be slow drying and prone to sagging during application and to solvent popping during baking under high humidity conditions. Application solids are much lower than comparable latex paints.

The emulsion or latex paints have employed as their sole or principal binder polymer a polymer of very high molecular weight, i.e., in the range of about 100,000 to about l,000,000 or higher. Such paints have been characterized by rapid drying and comparatively low gloss relative to paints based on water-soluble polymers.

Water-soluble polymers of high molecular weight have been added to latex paints as thickeners. Characteristically, such thickener polymers are used in very small amounts, e.g., of the order of one percent.

THE INVENTION It has been discovered that water-based paints having a superior combination of physical properties and application characteristics can be obtained by using certain novel combinations of solution polymers and emulsion polymers. The coatings obtained from these hybrid compositions exhibit high gloss and generally excellent appearance.

The hybrid, water-based, paint compositions of this invention employ in combination a low molecular weight emulsion polymer and a low molecular weight solution polymer with the latter being present in an amount sufficient to contribute significantly to the composition of the polymeric binder, i.e., at least about weight percent of this polymeric combination. Thus, they differ from the conventional emulsion type paints employing a water-soluble thickener polymer in at least three compositional respects irrespective of chemical functionality, namely, l the emulsion polymers of the instant paints have significantly lower molecular weights, (2) the solution polymers of the instant paints have significantly lower molecular weights, and (3) the solution polymers of the instant paints are employed in significantly higher concentrations than are the watersoluble thickener polymers.

More specifically, the hybrid paint compositions of this invention, exclusive of optional components such as pigments, particulate fillers and catalysts, have a liquid continuous aqueous phase. About 30 to about 50 percent by weight of this phase, exclusive of the aforecited optional components, is made up of a mixture of (a) an amino resin crosslinking agent; (b) a mixture of at least two copolymers of acrylic monomers; and (c) an amine. The balance is water or, in certain embodiments, water and an organic solvent. The mixture of copolyme rs comprises l about 5 to about 50, preferably about l0 to about 30, parts by weight ofa solution polymer." a carboxy-functional copolymer of acrylic monomers that (i) is at least partially neutralized with an amine, (ii) is soluble in said aqueous phase, (iii) has average molecular weight (M,.) in the range of about 3,000 to about 20,000. and (iv) has Tg in the range of-l 5 to 50C.. and (2) about 50 to about 95. preferably about 60 to about 90, parts by weight of an emulsion polymer," i.e., a copolymer of acrylic monomers having carboxy, hydroxy or carboxy and hydroxy functionality that (i) is essentially insoluble in said continuous phase, (ii) has average molecular weight (M in the range of about 3,000 to about 20,000 and (iii) has Tg of -IS to 50C. The amino resin crosslinking agent is present in an amount in the range of about 15 to about 35 weight percent of the sum of the weight of solution polymer and the weight of emulsion polymer. The amine is a water-soluble amine and is present in an amount sufficient to solubilize the solution polymer in the aqueous phase at a pH range of about 7.1 to about 8.5. In certain embodiments, he reinafter illustrated, these hybrid compositions include organic cosolvents while in other embodiments such solvents are not present.

when applied to the substrate to be coated by spraying, these water-based paints including pigments, par ticulate fillers, and catalysts, if any, contain between about 50 and about 65 percent by weight water or in those embodiments wherein such solvents are used, water and organic cosolvents.

PAINT PREPARATION A number of methods can be used to prepare the water-based paints of this invention.

In a first general method, at least one of the polymers, usually the solution polymer, is polymerized in solution in a water miscible or dilutable organic solvent while the other polymer, usually the emulsion polymer, is prepared by an emulsion polymerization in water. The resultant water-based paint will contain a conventional, essentially non-reactive, water-miscible or dilutable organic paint solvent. The concentration of organic solvent in such paints will be at least about 5 percent by volume of the volatile phase, i.e., organic solvent and water, and preferably in the range of about 10 to about 20 volume percent of the volatile phase.

In a second general method both the solution polymer and the emulsion polymer are prepared by emulsion polymerization in water. The paints thus prepared are prepared without organic solvents and thus employed free of same. Organic solvents in the amounts used in the first general method may be added to the dispersion, if desired.

A third general method is the same as the first general method except for the difference that in carrying out the emulsion polymerization the surfactant, i.e., surface active agent or emulsifier, is replaced by a solution polymer hereinafter more fully described.

A fourth general method is the same as the second general method except for the difference that in carrying out one or both, preferably both, of the emulsion polymerizations the surfactant is replaced by a solution polymer hereinafter more fully described.

The advantage provided by the third and fourth general methods is that elimination of the conventional surfactant eliminates the problem of incompatibility and water sensitivity associated with the use of surfactants.

POLYMER COMPOSITION IN DETAIL A. The solution polymer in these paints has carboxy functionality and may also have hydroxy functionality and/or amide functionality. These polymers contain about 5 to about 30 mole percent of acrylic or methacrylic acid and 70 to 95 mole percent of olefinically unsaturated monomers copolymerizable with such acid component. Preferably, these other olefinically unsaturated monomers are monoacrylates or monomethacrylates. In the embodiment wherein the primary solution polymer has only carboxy functionality, these are preferably esters of acrylic acid or methacrylic acid and a C C monohydric alcohol. C C monovinyl hydrocarbons such as styrene, alpha methyl styrene, t-butyl styrene, and vinyl toluene may comprise up to about 30 mole percent of such polymer. Vinyl monomers such as vinyl chloride, acrylonitrile, methacrylonitrile and vinyl acetate may be included in the copolymer as modifying monomers. However, when employed, these modifying monomers should constitute only between about and about 30, preferably 0 to about l5, mole percent of such polymer. In the embodiment wherein the solution polymer has both carboxy functionality and hydroxy functionality, the copolymer contains about to about 25 mole percent of acrylic of methacrylic acid, about 5 to about 25 mole percent of a hydroxyalkylacrylate or methacrylate, e.g., hydroxyethyl acrylate, hydroxyproyl acrylate, hydroxyethyl methacrylate or hydroxyprol methacrylate, and a remainder of the same monoctional monomers as set forth above for the solely carboxy-functional polymer. In still another embodiment, the polymer has amide functionality in addition to carboxy functionality. Such a polymer contains about 5 to about 25 mole percent acrylic acid or methacrylic acid, about 5 to about 25 mole percent of acrylamide, methaerylamide, N-methylolacrylamide, N- methylolme'thacrylamide, or the alkyl ether of a methylolacrylamide or a methylolmethacrylamide, e.g., N- isobutoxymethylolacrylamide, with the remainder of the same monofunctional monomers as set forth above for the solely carboxy-functional polymer. A portion of the amide functional monomer may be replaced with an equimolar amount of one of the aforementioned hydroxyacrylates or hydroxymethacrylates.

Other monomers not heretofore mentioned may be used in these polymers if used in limited concentra tions. These include Z-acrylamido-Z-methylpropanesulfonic acid and methacryloyloxyethylphosphate, which may comprise up to about 3 percent of such polymer.

B. The emulsion polymer in these paints has carboxy functionality, hydroxy functionality or carboxy and hydroxy functionality. These polymers contain 0 to mole percent acrylic acid or methacrylic acid, preferably 0 to l0 mole percent, and 85 to I00 mole percent of other olefinically unsaturated monomers that are copolymerizable with each other and with the acid component when the latter is used. Such other olefinically unsaturated monomers are the same in type and of the same percentage distribution range as those heretofore disclosed for the solution polymer with the exception of the acid monomer content above noted.

In those embodiments, wherein both the solution polymer and the emulsion polymer have hydroxy functionality and carboxy functionality, it is preferred to have a greater concentration of carboxy functionality on the solution polymer relative to the emulsion polymer and a greater concentration of the hydroxy functionality on the emulsion polymer relative to the solution polymer.

Thus, the combinations involved include (a) a car boxy-functional solution polymer and a hydroxy-functional emulsion polymer, (b) a carboxy-functional solution polymer and a carboxy-functional emulsion polymer, (c) a carboxy-functional solution polymer and a carboxy-functional, hydroxy-functional emulsion polymer, (d) a carboxy-functional and hydroxy-functional solution polymer and a hydroxy-functional emulsion polymer, (e) a carboxy-functional, hydroxy-functional solution polymer and a carboxy-functional and hydroxy-functional emulsion polymer, (f) a carboxyfunctional and amide-functional solution polymer and a hydroxy-functional emulsion polymer, (g) a carboxyfunctional and amide-functional solution polymer and a carboxy-functional emulsion polymer, (h) a carboxyfunctional and amide-functional solution polymer and a carboxy-functional and hydroxy-functional emulsion polymer, (i) a carboxy-functional, hydroxy-functional, and amide-functional solution polymer and a hydroxyfunctional emulsion polymer, (j) a carboxy-functional, hydroxy-functional, amide-functional solution polymer and a carboxy-functional emulsion polymer, and (k) a carboxy-functional, hydroxy-functional, amide-functional solution polymer and a carboxy-functional, hydroxy-functional emulsion polymer. Amide functionality may also be incorporated into the emulsion polymer but this is more difficult to achieve efficiently that in the solution polymer, particularly in the case of modifled amide functionality, e.g., N-methylolacrylamide.

C. The amino resin crosslinking agent, may be and is hereafter illustrated as a conventional amino resin crosslinking agent of the type long in use as a crosslinking agent of the type long in use as a crosslinking agent in acrylic enamels, e.g., melamine-formaldehyde resins and urea-formaldehyde resins.

DETAILED DESCRIPTION OF FIRST GENERAL METHOD FOR PREPARING PAINTS DESCRIBED HEREIN a. Preparation of Solution Copolymer In preparing the water-soluble copolymer, the functional monomers and the remaining monoethylenically unsaturated monomers are mixed and reacted by conventional free radical initiated polymerization in such proportions as to obtain the copolymer desired. A large number of free radical initiators are known to the art and are suitable for this purpose. These include benzoyl peroxide; t-butyl peroctoate; t-butyl perbenzoate; lauryl peroxide; t-butyl-hydroxy peroxide; acetylcyclohexane sulfonyl peroxide; diisobutyryl peroxide; di-(2- ethylhexyl) peroxydicarbonate; diisopropyl peroxydicarbonate; t-butylperoxypivalate; decanoyl peroxide; azobis (2-methyl propionitrile etc. The polymerization is carried out in solution using a solvent which is miscible or dilutable with water. The solvent concentration at this stage is ordinarily about 30 to 60 weight percent of the polymerization solution. The polymerization is carried out at a temperature between about 45C. and the reflux temperature of the reaction mixture. Included among the suitable solvents are n-propyl alcohol, isopropyl alcohol, dioxane, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, etc. The copolymer thus obtained is neutralized with amine to a pH of about 6 to 10 and diluted to desired viscosity with water or organic solvent.

b. Preparation of Emulsion Copolymer In preparing the emulsion copolymer, the functional monomers are mixed and reacted by conventional freeradical initiated polymerization in aqueous emulsion to obtain the copolymer desired.

Coventional surfactants, chain transfer agents, and initiators are employed in the emulsion polymerization. The monomer charge is usually emulsified by one or more micelleforming compounds composed ofa hydrophobic part, such as a hydrocarbon group containing six or more carbon atoms, and a hydrophilic part, such as hydroxyl groups, alkali metal, ammonium carboxylate groups, sulfonate groups, phosphate or sulfate partial ester groups, or a polyether chain. Exemplary emulsifying agents include alkali metal sulfonates of styrene, naphthalene, decyl benzene, and dodecyl benzene; sodium dodecyl sulfate; sodium stearate; sodium oleate; the sodium alkyl aryl polyether sulfates and phosphates; the ethylene oxide condensates of long chain fatty acids, alcohols, and mercaptans, and the alkali metal salts of rosin acids. These materials and the techniques of their employment in emulsion formation and maintenance are well known in the art. A chain transfer agent or mixture of chain transfer agents may be added to the reaction medium to limit the molecular weight of the copolymer; such chain transfer agents are generally mercaptans such as dodecanethiol, benzenethiol, loctanethiol, pentanethiol, and butanethiol. These are conventional materials and are employed in a conventional manner. The polymerization initiator is composed of one or more water-soluble, free-radicalgenerating species such as hydrogen peroxide or the sodium, potassium, or ammonium persulfates, perborates, peracetates, percarbonates and the like. The polymerization is carried out at a temperature between about 45C. and the reflux temperature of the reaction mixture. As is well known is the art, these initiators may be associated with activating systems such as redox systems which may incorporate mild reducing agents, such as sulfites and thiosulfites, and redox reaction promoters such as transistion metal ions, and that these allow the polymerization to be carried out at a lower temperature, e.g., 0C. or below. As, however, it is desirable to maintain a low concentration of non-polymeric ionic species in the finished paint formulation in order that the cured paint film may have optimum resistance to water, it is preferred to use a minimum concentration of such optional inorganic salts as ferrous sulfate, sodium bisulfite, and the like.

Those skilled in the art will be aware that other emulsifying agents, polymerization initiators and chain transfer agents may be used which are compatible with the polymerization system herein required and with the attainment of acceptable cured paint film properties.

As will be disclosed later herein, the solution polymer may also be prepared by emulsion polymerization. In such preparation, the resultant acid-functional copolymer latex is converted to a polymer solution by the addition of an appropriate base, usually ammonia or an organic amine. There are, however, different needs involved in the after-preparation employment of the emulsion polymer that is used as such in formulation of 6 paint and the solution polymer which although prepared by emulsion polymerization is subsequently converted to a solution polymer and used as such. These needs should be taken into consideration in the preparation procedure.

In the use of emulsion polymerization to produce a solution polymer, there is no need for the resulting latex to be stable under conditions different from those ensuing at the end of the polymerization process since the latex no longer exists, as such, after the polymer goes into solution upon neutralization. To facilitate such conversion to solution polymers, polymers prepared by emulsion polymerization for use as solution polymers ordinarily contain a higher concentration of carboxyl groups and a lower concentration of decidedly hydrophobic monomers, e.g., 2-ethylhexyl acrylate, relative to the corresponding concentrations in the polymers prepared by emulsion polymerization for use as such.

In contrast, latices which are used as such in the formulation of paint are required to remain essentially as stable latices throughout the processes of polymerization, paint formulation, and product distribution and use This implies a requirement of stability, i.e., freedom from coagulum formation through time and under a variety of pH conditions, solvent environment, etc. These requirements are best met, and hence it is preferred to use, an alkali metal or ammonium persulfate either as the sole polymerization initiator, or as one constituent of a mixed initiator system. In those embodiments in which conventional surfactants are used, it is preferred to use a plurality of surfactants, more specifically a combination of anionic and nonionic surfactants, to obtain a more stable latex. Such surfactant mixtures are well known in the art.

c. Formulation of Paint The polymer solution and the polymer latex prepared according to the aforedescribed procedures are subsequently converted into a paint using conventional paint formulation techniques. Typically, a mill base is prepared which comprises the bulk of the pigment and/or particulate filler of the paint formulation. The mill base is let down" i.e., blended with the remainding polymeric and liquid constituents of the final formulation. A mill base, prepared by conventional sand grinding, ball milling, or pebble milling generally comprises all or a part of the water soluble resin, pigments, organic cosolvents, and may also comprise a quantity of amine in excess of that required to solubilize the solution polymer. To complete the paint, the polymer latex which has been neutralized to a pH range of 5.0 to 10, preferably 5 to 9, is added with mild agitation to the balance of the water required in the total formulation. The balance of the water-soluble resin, crosslinking agent, and millbase are added slowly with agitation. Additional quantities of pigment may be added subsequently as slurries in organic solvents or as separate mill bases to adjust the color as desired. The viscosity of the finished paint is determined and adjusted as required to obtain desired application properties.

Alternately, all or a portion of the (preferably neutralized) polymer latex, water, organic cosolvent, and amine may be added to the solution polymer and pigments prior to ball milling, sand grinding, or pebble milling. This procedure is advantageously employed to reduce the viscosity of mill bases prepared using the solution polymers of relatively high molecular weight.

d. Use of Organic amines Organic amines are used to neutralize carboxyl groups on the solution polymer and hence to render it soluble in the aqueous dispersion. They are also used to maintain the pH of the finished paint formulation above about 7, e.g.. in the range of 7 10, preferably between 7 and 9.5, and with certain pigments such as aluminum flakes preferably between 7 and 9, to prevent premature reaction of the functional groups on the acrylic copolymer with the amino resin crosslinking agent. Those skilled in the art will be aware that in certain embodiments the paint dispersion can be made up at a pH outside the pH range for application and later adjusted to the desired pH shortly before it is applied. A portion of the amine, e.g., preferably between about 60 and I percent of the amount chemically equivalent to the carboxyl functionality of the polymer is added to the solution polymer directly. Advantageously, a small additional portion of amine is used to raise the pH of the emulsion polymer to about to about 10, preferably 5 to 9, prior to finishing the paint formulation so that the mill base is not subjected to the low pH environment of the polymer latex (pH about 2.5).

Suitable amines are amines (l) which are soluble in the aqueous medium of the paint, (2) that ionize sufficiently in such aqueous medium to solubilize the solution polymer, (3) that ionize sufficiently in such aqueous medium when employed in suitable amounts to provide the paint dispersion with a pH of at least about 7, preferably 7.2 or higher, and thereby keep the rate of reaction between reactive groups of the amino resin (crosslinking agent) negligible prior to curing, and (4) that allow for rapid curing of the enamel upon heating. Suitable amines include alkyl, alkanol and aryl primary, secondary and tertiary amines. Preferred are secondary and tertiaryalkyl and alkanol amines having a boiling point within the range of 80 200C. By way of example, these include N,N-dimethyl ethanolamine, N,N- diethylethanolamine, isopropanolamine, morpholine, N-methyl-morpholine, N-ethylmorpholine, N-methylethanolamine, 2,6-dimethylmorpholine, methoxypropylamine, and 2-amino-2-methyl-l-propanol.

e. Catalysts Catalysts for the curing of resins described herein are not normally required to obtain satisfactory film properties. If desired, however, for purposes of lowering the film baking temperature or of further improving cured film properties, strong acid catalysts can be employed in an amount not in excess of 3 percent by weight of the total finished paint formulation. Sais strong acid catalysts may be introduced either as copolymerizable species incorporated in one or both acrylic copolymers, e.g., Z-acryIamide-Z-methylpropanesulfonic acid, or as a non-polymerizable additive, e.g., p-toluenesulfonic acid. It is generally preferred not to add such catalysts, however, as they may tend to increase the water sensitivity of the cured film and may deleteriously affect storage stability of the liquid paint.

f. Cosolvents In those embodiments wherein a volatile organic solvent is employed as a cosolvent, i.e., solution ofthe solution polymer also being effected by the use of a water-soluble amine, the following solvents are suitable for this use include: n-propyl alcohol, isopropyl alcohol, butanol, 2'butoxyethanol. 2(2-butoxy)ethoxyethanol, n-octyl alcohol, dioxane, ethylene glycol monomethyl ether. ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, etc.

DETAILED DESCRIPTION OF SECOND GENERAL METHOD FOR PREPARING PAINTS DESCRIBED HEREIN a. Preparation of Solution Polymer In this method, the watersoluble copolymer is produced by emulsion polymerization. The functional monomers are mixed and reacted by conventional freradical initiated polymerization in aqueous emulsion to obtain the copolymer desired. The resulting acid-functional copolymer latex is converted to a polymer solution by the addition of an appropriate base, usually ammonia or an organic amine.

Conventional surfactants, chain transfer agents, and initiators are employed in the emulsion polymerization. The monomer charge is usually emulsified by one or more micelleforming compounds composed of a hydrophobic part, such as a hydrocarbon group containing sic or more carbon atoms, and a hydrophilic part, such as hydroxyl group, alkali metal or ammonium carboxylate groups, phosphate or sulfate partial ester groups, sulfonate groups, or a polyether chain. Exemplary emulsifying agents include alkali metal sulfonates of styrene, naphthalene, decyl benzene and dodecyl benzene; sodium dodecyl sulfate; sodium stearate; sodium oleate, the sodium alkyl aryl polyether or sulfates and phosphates; the ethylene oxide condensates of long chain fatty acids, alcohols, and mercaptans, and the alkali metal salts of rosin acids. These materials and the techniques of their employment in emulsion formation and maintenance are well known in the art. As previously pointed out, however, when emulsion polymerization is used to produce a solution polymer, there is no need for the resulting latex to be stable under conditions different from those ensuing at the end of the polymerization process since the latex no longer exists as such after the polymer goes into solution upon neutralization. To facilitate such conversion to solution polymers, polymers prepared by emulsion polymerization for use as a solution polymer ordinarily contain a higher concentration of carboxyl groups and a lower concentration of decidedly hydrophobic monomers, e.g., 2-ethylhexyl acrylate, relative to the corresponding concentrations in the polymers prepared for use as emulsion polymers. Further, the teaching hereinbefore set forth with respect to the choice of initiators when preparing the latter, i.e., using an alkali metal or ammonium persulfate either as the sole polymerization initiator or as one constituent of a mixed initiator system to avoid coagulum formation through time and under a variety of pH conditions, solvent environment, etc., is applicable where the polymer is to be converted to a solution polymer. Such initiators may be used when preparing the solution polymer by emulsion polymerization but conventional peroxide initiators are quite suitable for this. Hence, this method offers an advantage, in this respect, in that the concentration of ionic inorganic contaminants, e.g., sulfate ions, in the paint formulation is reduced. A chain transfer agent or mixture of chain transfer agents may be added to the reaction medium to limit the molecular weight of the polymer, such chain transfer agents are generally mercaptans such as dodecanethiol, benzenethiol, l-octanethiol, pentanethiol and butanethiol. These are conventional materials employed in a conventional manner. The polymerization initiator is composed of one or more water-soluble, free-radical-generating species such as hydrogen peroxide or the sodium, potassium or ammonium persulfates, perborates, peracetates, percarbonates and the like. As is well known in the art, these initiators may be associated with activating systems such as redox system which may incorporate mild reducing agents, such as sulfites and thiosulfites and redox reaction promoters such as transition metal ions. As hereinbefore mentioned, however, it is desirable to maintain a low concentration of non-polymeric ionic species in the finished paint formulation in order that the cured paint film may have optimium resistance to water. Hence, it is preferred to use a minimum concentration of such optional inorganic salts as ferrous sulfte, sodium bisulfite, and the like. Those skilled in the art will be aware that other emulsifying agents, polymerization initiators and chain transfer agents may be used which are compatible with the polymerization system herein required and with the attainment of acceptable cured paint film properties.

b. Preparation of Emulsion Copolymer The emulsion copolymer may be prepared using the same procedures hereinbefore recited for preparation of the emulsion copolymer in part (b) of the first general method.

c. Formulation of Paint The polymer solution and the polymer latex prepared according to the aforedescribed procedures may be subsequently converted into a paint using the same procedures hereinbefore recited for formulation of paint in part (c) of the first general method.

d. Use of Organic Amines The use of organic amines and amines which are suitable for such use are the same for this general method as hereinbefore described in detail in part (d) of the first general method.

e. Catalysts The use of catalysts and catalysts which are suitable for curing the resins hereinbefore described and hereinafter illustrated are the same for this general method as hereinbefore described in detail in part (d) of the first general method.

f. Cosolvents The use and choice of cosolvents for use with this general method may be the same as hereinbefore described in part (f) of the first general method.

DETAILED DESCRIPTION OF THIRD GENERAL METHOD FOR PREPARING PAINTS DESCRIBED HEREIN The third general method for preparing the paints disclosed herein is identical with the first general method hereinbefore described in detail except for the difference that all or a part of the surfactant, i.e., surface active agent or emulsifier, employed in preparing the emulsion polymer, is replaced with a stabilizer poly- 10 mer, that is identical with or similar to, the solution polymer heretofore described in the first and second general methods and employed as a primary constituent of the paints described herein.

The stabilizer polymer of the third and fourth general methods is carboxy functional and soluble in the aqueous phase of these paint dispersions and is either the same as the primary solution polymer, heretofore discussed, or similar to such solution polymer and compatible with the system. The average molecular weight (FA of the stabilizer polymer may be the same as that of the primary solution polymer, i.e., between 3,000 and 20,000 but advisedly is of lower molecular weight than the primary solution polymer. Preferably, the average molecular weight of this third copolymer is in the range of about 3,000 to about 8,000. Its Tg is in the range of-l5" to 50C. When the stabilizer polymer is used in lieu of the surfactant to prepare either the solution polymer or the emulsion polymer, it is present in a concentration in the range of about 0.2 to about l0, preferably about 0.5 to about 5, weight percent based on the weight of polymer to be prepared.

The stabilizer polymer may be prepared by any of several methods, including l the method used to prepare the solution polymer of the first general method of paint preparation, i.e., polymerization in solution in a water miscible or dilutable organic solvent; (2) the method used to prepare the solution polymer for the second general method of paint preparation, i.e., emulsion polymerization using an emulsifier or surfactant; (3) emulsion polymerization using in lieu of a surfactant a small amount of the intended polymer from a previous preparation; and (4) a method of emulsion polymerization described hereinafter which employs neither surfactant nor a water soluble polymer in lieu thereof. In the latter, conventional chain transfer agents and polymerization initiators are used as described hereinbefore for the preparation of a solution polymer by emulsion polymerization. A mixture of monomers including carboxyl functional monomers and a chain transfer agent is added slowly to a stirred mixture of initiator and water maintained at a suitable reaction temperature, e.g., between 45 and C. It is preferred to add simultaneously with the monomer mixture an additional quantity of polymerization initiator to sustain a sufficient initiator concentration throughout the polymerization. The polymer latex so obtained is filtered and neutralized with ammonia or water-soluble amine to render it water soluble.

DETAILED DESCRIPTION OF FOURTH GENERAL METHOD FOR PREPARING PAINTS DESCRIBED HEREIN The fourth general method for preparing the paints disclosed herein is identical with the second general method hereinbefore described in detail except for the difference that all or a part of the surfactant used to prepare the solution polymer, the emulsion polymer or, preferably, both the solution polymer and the emulsion polymer is replaced by a stabilizer polymer, such as heretofore described in detail in the description of the third general method.

This invention will be more fully understood from the following illustrative examples:

EXAMPLE 1 A heat-curable coating composition suitable for automotive topcoat application is prepared from an aque- 11 ous acrylic copolymer latex, an aqueous solution of a second acrylic copolymer. and an amino resin crosslinking agent, here a melamine resin, in the manner hereinafter set forth:

"'- product of Rohm and Haas Company. characterized as an anionic surfactant containing 23'! active component described as the sodium salt of an alltyl aryl polyether sull'onate.

"*a product of Rohm and Haas Company. characterized as u nonionic surfactant containing 70% active component described as an ulltylarylpolyether alcohol aver- 25 aging ethylene oxide units per molecule.

The reactor charge is heated to 50C. in a reaction vessel equipped for a stirrer, reflux condenser, nitrogen inlet type, addition funnel and theremometer. The 30 monomer mixture is mixed with the listed additives and an emulsion is formed by stirring. The monomer emulsion is added over a four and one-half hour period. The temperature is maintained at 50 t 5C throughout the monomer addition and for 2 hours thereafter. A nitrogen sparge is maintained throughout. The latex so formed is cooled to room temperature, filtered, and formulated into paint as hereinafter described. The molecular weight of the polymer so prepared (M is about 6,000. lts glass transition temperature, Tg, is about 14C (calculated from the monomeric composition without regard to molecular weight as are all Tg values herein given).

STEP ll PREPARATION OF WATER SOLUBLE ACRYLIC POLYMER Monomer Mixture and Initiator Parts by Weight methacrylic acid l5.0 methylmethacrylate l 5.0 styrene 20.0 butyl acrylate 40.0 butyl methacrylate 10.0 t-butylperoctoate 3 .5 Reactor Charge isopropyl alcohol 45 12 solids with wate The polymer thus prepared has molecular weight (M,,) of about 9.200. The glass transition temperature of this polymer is about 18C.

STEP [[1 FORMULATION OF PAINT A mill base is prepared by pebble milling together the following materials:

Components Parts by Weight polymer solution from Step 2 5.5 titanium dioxide pigment l3.8 Water 3.3

An enamel is then prepared by blending this mill base with the following materials:

Components Parts by Weight latex from Step I 42.5 Water 19.0 isopropanol l .0 propylene glycol 5.1 melamine crosslinlting agent.

Cymel 300" 4.6

l0% aqueous dimethylethanolamine L4 l0% aqueous p-toluenesulfonic acid 3.8

"'a product of American C, C and a grade of thoxymethylmelamine. "'the solution is adjusted to pH 8 by addition of dimethylaminoethanol.

The enamel so obtained is reduced with water to spray viscosity (20 seconds Ford Cup No. 4 follows ASTM D-l200), applied to primed steel panels, i.e., mild steel panels to which has been applied a standard epoxy type automotive primer, by spraying and cured for 20 minutes at C. The cured film has a 20 gloss of 75, determined by ASTM D-523. This film demonstrates no visible change after soaking in water at 32C for 240 hours. This film displays excellent solvent resistance'. The film flexibility and hardness are suitable for automobile topcoats.

EXAMPLE 2 The procedures of Example l are repeated with the following differences: (1) the monomer emulsion of Step I is prepared from the following reactant monomers and chain transfer agent, all other materials employed in preparing the latex being the same in kind and quantity as in Example 1:

Materials Parts by Weight methyl methacrylate 49.0 methacrylic acid 5.0 ethyl acrylate l6.0 butyl acrylate 30.0 I -octanethiol 0.4

The molecular weight of this polymer (T1,) is about l3,300 and has a glass transition temperature of about 20C.

A paint is formulated according to the procedures of Example I using the following components:

The molecular weight of this polymer (Mn) is about Compnnunls P n b w i h and its is about 32C.

Mill Base Let Down EXAMPLE 6 latex from Step I 44.0 vnlyrgcrwlution fmm 5 The procedures of Example 2 are repeated with the f agdioxide pigmcm 2; single difference that, inthe preparation of the emul- Water 7 40 21.0 sion polymer in Step I, the monomer emulsion is predtmethyl- 4 pared from the following reactant monomers and chain isupropyl a'mhoi transfer agent, all other materials employed in preparn-hutanol m 4.0 ing the latex being the same in kind and quantity as in Examples l and 2.

'defined in Example I M t l P t b w ht The resultant paint is ad usted to 25 seconds Ford a was s y mg Cup No. 4 viscosity by addition of water, applied to many i methacryhc acid 7.0 primed steel panels, and sub ected to a twenty-minute styrene 20.0 bake cycle at temperatures moving upward from 80C g y: melll'acrylaw igg to l80C and remaining at 180C lasting for about 10 f l ff i' f minutes.

EXAMPLE 3 The molecular weight of this polymer (M is about The procedures of Example 2 are repeated with the 13,000 d i T i about 40C single difference that, in the preparation of the emulsion polymer in Step I, the monomer emulsion is pre- EXAMPLE 7 pared from the following reactant monomers and chain A heat-curable coating composition is prepared in transfer agent, all other materials employed in preparthe following manner: ing the latex being the same in kind and quantity as in Examples 1 and 2 STEP 1 PREPARATION OF THE ACRYLIC COPOLYMER LATEX Materials Parts by Weight Monomers and Additives Parts by Weight methyl mcthacrylate 49.0 styrene 20.0 mcthacrylic acid 5.0 hydl'oxypropylmethacrylate [8.0 ethyl acrylate 16.0 2-ethyl hexyl acrylate 20.0 butyl acrylate 30.0 butyl methacrylate 30.0 l-octanethiol 0.2 acrylic acid 2.0 methyl methacrylate 100 Water 900 loctanethiol 0. 5 Triton x-zoo 1.2 The molecular weight of this polymer (M IS about Trim X40512 36 l7,500 and its Tg 18 about 20 C. 40 potassium lfm 0,4

Reactor Charge Water 60.0 E M LE 4 Triton X-200'" 1.7 potassium persulfate 0. l The procedures of Example 2 are repeated with the "del'lned in Example I single difference that, m the preparation of the emulunarmed in Example i sion polymer in Step I, there is used 0.1 parts by weight of l-octanethiol, all other materials employed in preh h h d H b paring the latex being the same in kind and quantity as T e c arge cam qulc y to mg a in Example 2 cooled to 95 C. The reactant monomers are mixed with The molecular weight of this polymer (Mn) is about so the listed additives and an emulsion is formed by stir- 24 000 and its Tg is about ring. The monomer emulsion IS then added to the hot reactor charge over a two-hour period. The temperature is maintained at about 90C during and for two EXAMPLE 5 hours following the addition of the monomer emulsion. The procedures of Example 2 are repeated with the The latex is'ccloled 9 room 'f p i filtered difference that, in the preparation of the emulsion polyformulated a P as hel'emaftel' This mer in Step I, the monomer emulsion is prepared from P y has average molecular welsh! n) of about 0 the following reactant monomers and chain transfer and a 8 of about 15 agent, all other materials employed in preparing the STEP PREPARATION OF WATER SOLUBLE latex being the same In kind and quantity as m Exam- 0 ACRYLIC POLYMER pics I and 2.

A water-soluble, acrylic copolymer IS prepared from the following materials:

Materials Parts by Weight methyl mehacrylale 50.0 5 Monomer Mixture and Initiator Parts by Weight methacrylic acid 5.0 s

yrene l5.0 223:1: hydroxypropylmethacrylate N810 acrylic acid .0 llouanemlol bulyl methacrylate 37.0

-Continued Monomer Mixture and Initiator Parts by Weight Z-cthyl hcxyl acrylate methyl methacrylate t-hutyl pcrhcnzuatc Reactor Charge 2( Z-butyuxyethuxy) ethanol 43 M.) of about 5.000 and its Tg is about 17C. 20

STEP III FORMULATION OF PAINT A mill base is prepared by ball milling the following materials:

Materials Parts By Weight Polymer from Step II Titanium dioxide pigment Water An enamel is formulted by blending this mill base with the following materials:

Materials n butanol 2t Z-butoxyethoxy )ethanol latex from Step I I0% aqueous dimethylaminoethanol Water Parts by Weight "'a commercial grade of hexamethoxymetltylinelamine marketed by American Cyanamid Company.

The paint so obtained is reduced with water to spray viscosity 17 seconds, Ford Cup No. 4), applied to primed steel panels and subjected to a 30-minute bake cycle comprising ten minutes during which the temperature rises from 80 to 160C during the first 10 minutes and remains at I60C for 10 minutes. The cured film has a 20 gloss of 80, is unafiected by xylene (one minute exposure), or by exposure to water at 32C for 240 hours.

EXAMPLE 8 The procedures of Example 7 are repeated with the single difference that, in the preparation of the emulsion polymer in Step I, the monomer emulsion is pre' pared from the following reactant monomers and chain transfer agent, all other materials employed in preparing the latex being the same in kind and quantity as in Examples 1 2.

Materials Parts by Weight styrene methacrylic acid butyl ac rylate butyl methacrylatc Z-acrylamidc 2 methylpropane sulfonic acid I -octzincthio| This polymer has average molecular weight (M,,) of about 8,000 and a Tg of about 5C.

EXAMPLE 9 A heat-curable coating composition is prepared in the following manner:

STEP l PREPARATION OF ACRYLIC COPOLYMER LATEX Monomers and Additives Parts by Weight methyl methacrylate 48.0 methacrylic acid 7.0 ethyl aerylate 35.0 butyl acrylate 10.0 l-octanethiol 0.4 Triton X-200" 1.0 Triton X-305 4.5 Water ammonium persulfate 0.4 Reactor Charge Water 30 Triton X-200?" 2 ammonium persulfate 0.l

defined in Example lv "'defined in Example I.

The procedures of Step I, Example 1, are repeated to produce a latex of 40 percent solids. This polymer has average (M,,) of about 13,000 and a Tg of about 32C.

STEP II PREPARATION OF WATER SOLUBLE ACRYLIC POLYMER The procedures of Step II, Example 7 are duplicated.

STEP III FORMULATION OF PAINT A mill base is prepared by pebble milling together the following materials:

Materials Parts by Weight polymer solution of Step [I I 1.0 Cymel 300" 8.0 titanium dioxide pigment l9.7 isopropanol 4.0 n-butanol 5.0 Water 6.0

"'defined in Example I.

An enamel is prepared by blending this mill base with the following materials:

Materials Parts by Weight latex from Step I 55.0

I09? aqueous dimethylethanolamine 4.0 Water 13.0

I09? aqueous p-toluene sulfonic acid (neutralized with dimethylethanol amine) 0.6

EXAMPLE l0 The procedures of Example 1 are repeated with the single difference that in the preparation of the soluble polymer of Step II 2.5 parts t-butylperbenzoate are used in lieu of 3.5 parts of t-butylperoctoate. The polymer so obtained has average molecular weight (M of about 10.500.

EXAMPLE II The procedures of Example 7 are repeated with the single difference that in the preparation of the soluble polymer of Step ll, 3 parts t-butylperoctoate are used in lieu of 3 parts t-butyl perbenzoate. The polymer thus obtained has an average molecular weight (M,,) of '0 about 6,000.

EXAMPLE 12 The procedures of Example 9 are repeated with the difference that the water soluble resin of Step ll is prepared from the following materials:

Rcactant Monomers and Initiator Parts by Weight hydroxypropyl methacrylale l acrylic acid 8 styrene 2S 2-ethylhexylacrylate 26 butyl methacrylate 26 t-butylperbenzoate 3 Reactor Charge 2hutoxycthanol 43 The polymerization is carried out at temperatures between l20 and 135C. The polymer has an average molecular weight M of about 6,000.

EXAMPLE l3 The procedures of Example 12 are repeated with the difference that 5 parts of acrylonitrile are substituted for 5 parts of styrene.

EXAMPLE 14 The procedures of Example 7 are repeated with the difference that the water soluble resin is prepared from:

Monomer Reactants and Initiator Parts by Weight methyl methacrylate 50 ethyl acrylate 42 methacrylic acid 8 S-butyl peroctoate 3.5 Reactor Charge isopropanol 45 The polymerization is carried out at reflux following the procedures of Step II of Example I. The average molecular weight (M,,) of this polymer is about 9,000.

EXAMPLE The procedures of Example 7 are repeated with the difference that the water soluble resin is prepared from the following materials:

Monomer Reactants and Initiator Parts by Weight methacrylic acid 18 butyl acrylate 55 methyl methacrylate 27 AlBN" 3 Reactor Charge isopropanol 45 The polymerization is carried out at reflux following the procedures of Step I] of Example I. The polymer so obtained has average molecular weight of about 5.000 and a Tg of 2C.

EXAMPLE l6 The procedures of Example 15 are repeated with the difference that the soluble resin is prepared from the following materials:

Monomer Rcaetants and Initiator Parts by Weight hydroxypropyl methacrylate l0 methacrylic acid l0 butyl acrylate 55 methyl methacrylate 2S MEN 4 Reactor Charge isopropanol 45 The polymer thus obtained has average molecular weight (M,,) of about 4,000 and its Tg is about 1Ci EXAMPLE 17 The procedures of Example 15 are repeated with the difference that the water soluble resin is prepared from:

Monomer Reactants and Initiator Parts by Weight hydroxypropylmethacrylate 5 methacrylic acid l0 N-methylolacrylamidc 3 methyl methacrylate 37 butyl acrylate 30 butyl methacrylate 20 t-butyl peroctoate 3 Reactor Charge isopropanol 45 EXAMPLE l8 The procedures of Example 1 are repeated with the difference that the ratio of polymer obtained from the latex of Step I to that of the solution polymer of Step ll is varied as follows:

Polymer Parts by Weight A B C D E F polymer from latex 92 85 65 50 35 polymer from solution I5 25 35 50 65 EXAMPLE l9 The procedures of Example 1 are repeated with the differences that the formulation of paint is as follows:

Mill Base Parts by Weight "'a product of Monsanto Company and a water reducible methylated melamine resin supplied at 806i solids in isopropanol.

This enamel is cured by baking at 140C for 20 minutes.

In the preceding 19 examples, the water-based paint has been formulated from an amino resin cross-linking agent, a synthetic polymer latex and a polymer soluble in the aqueous phase with the latter prepared by solu tion polymerization in an alcohol or similar water dilutable organic solvent. All such paints retain some of this solvent.

In the eight examples immediately following, both the solution resin and the emulsion resin are prepared by emulsion polymerization. The paints thus prepared are free of organic solvent unless such solvent is deliberately added.

EXAMPLE 20 STEP I PREPARATION OF THE SOLUTION POLYMER An acrylic copolymer soluble in the aqueous phase of the water-based paint of which it later becomes a part is prepared from the following materials in the manner hereinafter described:

"'defined in Example l. "'defined in Example 2.

The reactor charge is heated quickly to boiling and cooled to 95C. A monomer emulsion is formed from the above by mixing and stirring. The monomer emulsion is added to the hot reactor charge over a 2-hour period. The temperature is maintained at 90 i 5C throughout the monomer addition period and for two hours after addition is complete. The Z-(dimethylamino) ethanol is added in an amount equivalent to the acid monomer incorporated in the polymer and the solids content is reduced with water to 30 percent by weight. The polymer (M,,) is about 5,000 and the Tg is calculated to be 25C.

STEP II PREPARATION OF THE EMULSION POLYMER An emulsion polymer is prepared following the procedure of Step I from the following reactant monomers and chain transfer agent, all other materials employed 20 in preparing this latex being the same in kind and quantity as in Example 1.

Materials Parts by Weight methyl methacrylate 48.0 mcthacrylic acid 7.0 ethyl acrylatc 35.0 butyl acrylate 10.0 I-octancthiol 0.4

The average molecular weight of this copolymer is about 10,000 and it has a Tg of about 40C.

STEP III FORMULATION OF PAINT (FREE OF ORGANIC SOLVENT) A mill base is prepared by pebble milling together the following materials:

Materials Parts by Weight polymer solution from Step I l8.4 Cymel 300" 6.7 titanium dioxide pigment 16.5 Water 8.3

"'defined in Example l.

An enamel is formulated by blending together the following materials:

Materials Parts by Weight latex from Step II 46.0

10% aqueous 2-(dimethylamino)ethanol 3.3

10% aqueous p-toluene sulfonic acid (neutralized with 2-(dimethylamino) ethanol) 08 mill base 49.9

EXAMPLE 21 The procedures of Example 20 are repeated with the following differences: (1) the reactant monomers and the chain transfer agent used in the monomer emulsion of Step II are as follows:

Reactant Monomers and Chain Transfer Agent Parts by Weight methyl methacrylate 49.0 methacrylic acid 5.0 butyl acrylate 30.0 ethyl acrylate I6.0 I -octanethiol 0. I

and (2) the reactor charge is heated up to 55 i 5C with nitrogen purging. The emulsified monomers are added for a period of four hours. Reaction is continued for another two hours with the temperature maintained at 55 5C. The latex thus obtained is cooled, filtered, and used in the formulation of a water-based enamel as in Example 20.

EXAMPLE 22 A series of water dilutable polymers are prepared as in Step I of Example 20 and employed in place of the water dilutable polymer of Step 1, Example 20 in the water-based paint described in Example 20. The procedures of preparation are the same as used in Step l of Example 20. The materials employed in preparing these solution polymers" and the molecular weights -continued Materials Parts by Weight ethanol l v "'defined in Example l.

The above enamel is sprayed on primed steel panels and glass transition temperatures 0f the resultant and baked for 25 minutes. The initial temperature of P y are Set forth below the bake is 80C and this is raised gradually to 180C Materials Polymer Designation A B C D E styrene 25 methyl methaerylate 50 45 35 35 methacrylic acid l0 l l5 l5 l5 butyl acrylate 30 40 5O 50 ethyl acrylate l0 butyl methacrylate 35 Triton x-200 2.8 2.8 Triton X 305 3.6 3.6 3.6 3.6 3.6 Aerosol 22" 2.4 2.4 2.4 l-oetanethiol l 1.5 2 L5 1 Properties of Polymer m.) 7500 5400 4000 5400 7500 Tg. "C 8 lo 25 s a "'Aerosol 22 is a product at American Cyanamid Company.

EXAMPLE 3 where the latter temperature is maintained for 10 min- A series of emulsion polymers are prepared as in Step The appearance Ofthe baked 'f and the Prop u of Example 20 and employed in place ofthe emulsion erties of the baited coating are essentially the same as polymer of Step ll, Example 20. The procedures are the those Obtamed Example same as used in Step II of Example 20. The materials employed in preparing these emulsion polymers" and the molecular weights and glass transition temperatures EXAMPLE 25 of the resultant copolymers are set forth in the following table:

A water-based enamel is prepared by mixing the following materials:

MATERIALS POLYMER DESIGNATTON A B C D E F G H l Styrene 20 25 25 20 20 20 20 20 2O Methyl Methacrylate 25 25 Methacrylic Acid 7 l0 7 7 l3 l5 l5 l5 Acrylic Acid 22 Butyl Aerylate 23 I5 20 23 50 55 50 Butyl Methacrylate 25 50 40 25 l7 l0 l0 l0 l5 Hydroxypropyl Methacrylate 8 t8 Z-Aerylamide 2 Methyl Propane Sulfonic Acid l 1 Triton X-200 2.9 2.9 2.9 2.9 2.9 2.9 Triton X-302 3.6 3.6 3.6 3.6 3.6 3.6 3.6 3.6 3.6 Aerosol 22 2.4 2.4 2.4 l-Octanethiol 0.2 l 0.4 0.4 0.7 0.7 0.7 0.5 0.8

PROPERTIES OF POLYMER M, I 7.500 7 .500 13.500 14,000 8,000 8.000 8,000 l0.000 7.600 Tg. C 33 3| 2'] 33 2 5 -6 5 0 EXAMPLE 24 Mill Base (prepared by ball milling) Parts by Weight water-based elnamel IS prepared by mixing the folpolymerunn of Example 22 (salmon lowing materials. polymer) 1&5 Cymet 301 7.6 titaniuim dioxide pigment I 0 Water 8.4 p s b Wei Other Materials (to let down) Mmenals at y g polymer "G" of Example 23 (emulsion) Mill Base (prepared by P y Pebble mining) 10% aqueous 2-(d|rnethylamrno)ethanol 2.9 polymer (solution polymer) 1 I V from Step I, Example 20 l 8.8 "I product of American Cyanamnd Company. and a commercial grade of hexame cymel 0") 4 6 65 thoxymethylmellmine. titanium dioxide pigment 16.9 Water 7.3 This enamel IS ad usted to a viscosity of l7-20 seeother onds (No. 4 Ford Cup), by adding water and sprayed polymer (emulsion polymer from 47.0 over primed steel panels. The coated steel panels are Example 2] 23 baked at 160C for 25 minutes. The baked coatings exhibit good gloss. good solvent resistance and retained their gloss and hardness after soaking in water at 32C for 240 hours.

EXAMPLE 26 A watenbased enamel is prepared by mixing the following materials:

Mill Base (prepared by ball milling) Parts by Weight Polymer A of Example 22 (solution polymer) 14.8 Cymel 300'" 4.5 titanium dioxide pigment 17.7 Water 9 Other Materials (to let down) polymer A" of Example 23 (emulsion polymer) 4'14 aqeuous 2(dimethylamino)ethanol 3.6

10% aqueous p-toluene sulfonic acid 'defined in Example 1.

This enamel is adjusted to a viscosity of seconds (No. 4 Ford Cup) by adding water, and sprayed over primed steel panels. These coatings are baked for minutes. The initial baking temperature is 80C and this is gradually raised to 180C where it is maintained for at least 10 minutes. These coatings exhibit good physical properties.

EXAMPLE 27 A water-based enamel is prepared by mixing the following materials:

Mill Base (prepared by ball milling) Parts by Weight Polymer 13'' of Example 22 (solution polymer 12.4 titanium dioxide pigment 16.3 Cymel 301" 8.3 Water 8.3 Other Materials (to let down) Polymer "I" of Example 23 (emulsion polymer) 45.6

10% 24dimethylamin0lethanol 9.1

defined in Example 25 This enamel is adjusted to a viscosity of 20 seconds (No. 4 Ford Cup) by adding water and sprayed on primed steel panels. The coated panels are baked at 160C for 25 minutes. The coatings thus obtained exhibit excellent gloss 80 at 20 and good solvent resistance.

The following examples illustrate method emdodiments wherein the paints of this invention are prepared by substituting for the surfactant used in the preceding examples a stabilizer polymer which is a solution polymer, i.e., a polymer that is soluble in the aqueous phase of the water-based paint. As aforementioned, this stabilizer polymer may be the same as the solution polymer which is a primary constituent of the paint or it may differ therefrom so long as it is crosslinkable with another polymer or crosslinking agent in the system and is otherwise compatible with the system. The average molecular weight of the stabilizer polymer may be the same as that of the primary solution polymer but preferably has lower molecular weight and most preferably has average molecule weight (M,,) in the range of about 3,000 to about 8,000. The stabilizer polymer will ordinarily be present in an amount in the range of about 0.5

24 to about 10 weight percent of the combined weights of emulsion polymerized polymers in the paint.

EXAMPLE 28 A waterbased paint is prepared from the following materials:

Step 1 Preparation of Stabilizer Polymer There is charged to a reactor 200 parts of water. The reactor charge is heated to boiling and then cooled to C. To the reactor charge is added Solution A, a solution of 0.1 parts of ammonium persulfate in 0.8 parts of water. A solution, hereinafter termed Solution B, is prepared from 0.4 parts of ammonium persulfate in 2.5 parts water. A reactant monomer and chain transfer agent mixture is formed from the following materials:

Materials Parts by Weight methyl methacrylate 35 methaerylic acid 15 butyl acrylate 50 l-octanethiol 2 Step 11 Preparation of Emulsion Polymer An emulsion polymer is produced by first preparing the following: (1) there is charged to the reactor 200 parts of water and 4.25 parts of the stabilizer polymer from Step 1; (2) the following materials are thoroughly mixed:

Materials Parts by Weight styrene 20.0 methacrylic acid 15.0 butyl acrylate 55.0 butyl methacrylate 10.0 l-oetanethiol 0.6

(3) there are dissolved in 0.5 parts of ammonium persulfate and one part of 2-acrylamide-2-methylpropanesulfonic acid in 2.5 parts of water; and (4) there is dissolved 0.2 parts of ammonium persulfate in 5 parts of water. After these are prepared the emulsion polymer is prepared using the procedure and conditions used to prepare the stabilizer polymer of Step L In such, the order of addition of the four above listed components is as follows: (4) is added to (1) in the reactor and (2) and (3) are added simultaneously to the mixture of 1 and (4).

Step III Preparation of the Solution Polymer The procedures and steps of Step ll of this example are repeated with the following employment of reactant monomers:

Materials Parts by Weight methyl methacrylate 35 methacrylic acid butyl acrylate 50 l-octanethiol 1 After this latex is cooled and filtered, it is neutralized with 2-(dimethy1amino)ethanol to the amount equivalent to the methacrylic acid constituent of the polymer.

Step 1V Preparation of the Organic Solvent-Free, Surfactant-Free Hybrid Water-Based Enamel Materials Parts by Weight solution polymer from Step 111 14.1 Cymel 300 6.5 titanium dioxide 16.1 Water 6.4

The above materials are ball milled for 16 hours and mixed (let down) with the following materials:

Materials Parts by Weight latex from Step 11 (includes both emulsion polymer and stabilizer polymer 1) 47.3 10% aqueous Z-(dimethylamino) ethanol 9.6

The enamel thus prepared is adjusted to a viscosity of 17-20 seconds (No. 4 Ford Cup) by adding water. It is sprayed on primed steel panels and baked for 25 minutes at 160C. The coatings thus obtained exhibit good appearance, gloss and solvent resistance.

EXAMPLE 29 A water-based enamel is prepared in from the following materials:

Step 1 Preparation of Latex (includes stabilizer) polymer and emulsion polymer) 1. There is charged to a reactor 127 parts of water and two parts of the stabilizer polymer prepared in Step 1 of Example 28.

2. The following reactant monomers and chain transfer agent are thoroughly mixed.

Materials Parts by Weight styrene 20.0 hydroxypropylmethacrylate 14.0 methacrylic acid 6.0 butyl acrylate 30.0 butyl methacrylate 30.0 l-octanethiol 0.6

26 with the solution of (3) over a 2-3 hour period. while the temperature is maintained. The temperature is maintained at C for 2 hours after the addition of monomers is complete. The latex so obtained is cooled and filtered.

Step [1 Coating Formulation The latex obtained in Step 1 of this example is substituted for the latex of Step 11 of Example 28 and a waterbased enamel is prepared using the procedures and other ingredients used to prepare the water-based enamel in Example 28.

EXAMPLE 30 The procedures of Example 28 are repeated with the difference that the solution resin (Step [11) is prepared from the following materials:

1. There is charged to the reactor 1 19 parts of water and 1.8 parts of the stabilizer polymer prepared in Step 1 of Example 28.

2. The following reactant monomers and chain transfer agent are thoroughly mixed.

Materials Parts by Weight butyl melhacrylate 10.0 methyl methacrylate 35.0 methacrylic acid 15.0 butyl acrylate 40.0 1 -octanethiol 1 .3

3. There is dissolved 0.5 part of ammonium persulfate in 25 parts of water.

4. There is dissolved 0.2 parts of ammonium persulfate in 5 parts of water.

After the latex preparation procedures of Example 28 are carried out and the resultant latex is cooled and filtered, the polymer is neutralized with water-soluble amine as in the preceding examples.

EXAMPLE 31 A surfactant-free hybrid water-based enamel containing organic solvent is prepared using the formulation procedures of Step IV of Example 28 with the following differences:

Materials Parts by Weight solution polymer from Example 1,

Step 11 7.6 Cymel 301" 7.0 titanium dioxide 17.4 isopropanol 2.8 n-butanol 3.5 latex from Example 28. Step 11 (emulsion polymer pluls stabilizer polymer 1) S 1.3 10% aqeuous Z-(dimethylamino) ethanol 10.4

"'defined in Example 25.

The enamel when adjusted by water to a viscosity of 20 seconds (Ford Cup No. 4) is sprayed in a conventional manner upon primed steel panels and baked for 30 minutes. The initial baking temperature is 80C. This temperature is gradually raised to C and held there for at least 10 of the 30 minutes.

EXAMPLE 32 Step I Preparation of Latex A latex is prepared according to the procedures of Step 11 of Example 28 using the following mixture of reactant monomers and chain transfer agent:

'"del'tned in Example 25.

Step II Preparation of Enamel There is prepared a surfactant-free, solvent-free, hybrid water-based enamel. The procedures used are those of Step IV of Example 28, but with the following materials:

Materials Parts by Weight solution polymer from Step Ill of Example 28 l titanium dioxide Water latex from Step I of this Example aqueous 2(dimethylamino)ethanol seesa NOUIWQN "'defined in Example 1.

This enamel is sprayed on primed steel panels and baked for 25 minutes at 160C.

EXAMPLE 33 Step 1 Preparation of Latex A latex is prepared in the following manner:

EXAMPLE 34 The procedures of Example 33 are repeated with the difference that the latex (let down) is prepared as follows:

l. There is charged to a reactor 127 parts of water and 2.84 parts of stabilizer polymer prepared from the materials and according to the procedures used in Example 28.

2. The following reactant monomers and chain transfer agent are thoroughly mixed.

Materials Parts by Weight styrene 20.0 methacrylic acid 15.0 butyl acrylate 55.0 butyl methacrylate 10.0 I -octanethiol 0.6

3. There is dissolved 0.4 parts of ammonium persulfate and 1.0 parts of 2-acrylamide-2-methylpropane sulfonic acid in 16.7 parts of water.

4. There is dissolved 0.1 parts of ammonium persulfate in 4.17 parts of water.

The latex is then prepared from the above materials using the procedures of Step II of Example 28.

EXAMPLE 35 A water-based enamel is produced in the following manner:

Step 1 Preparation of (let down) latex 1. There is charged to a reactor 128 parts of water and 2.67 parts of stabilizer polymer prepared from the materials and using the procedures of Step I of Example 28.

2. The following reactant monomers and chain transfer agent are thoroughly mixed.

y 1d. Tlsielre is chfargeg lto a reactor 127 part; of wager Materials Pans by weigh arts 0 sta 1 izer o mer re are as in x- 2 p p y p p styrene 20.0 ample hydroxypropylrnethaerylate 18.0 2. The following reactant monomers and chain transacrylic aciId 22.3

butyl acry ate fer agents are thoroughly mixed. mflhacrymc 350 l -octanethio1 0.6

Materials Parts by Weight slywflfl 3. There is dissolved 0.5 parts of ammonium persulhydroxypropylmethacrylate 18.0 f d l 0 f 2 I h I acrylic acid 2.0 so ate an parts 0 -acry amt e-2-met y propane butyl acrylate I 50.3 sulfonic acid in 16.7 parts of water. butyl methacry ate l0. Locmnelhiol 06 4. There IS dissolved 0.1 parts of ammonium persul- Step II Formulation of Coating Material The procedures of Step [V of Example 28 are repeated substituting the latex prepared in Step 1 of this example for the latex prepared in Step [I of Example 28.

fate in 4.17 parts of water.

The latex is prepared using the above materials and the procedures of Step 11 of Example 28.

Step 11 Preparation of the Solution Polymer Materials Parts by Weight methyl methacrylate 35 mcthacrylic acid 15 butyl acrylatc 50 1 -octancthi0| 1 29 The solution polymer is then prepared from the above materials using the procedures used in Step II of Example 28.

The latex so obtained is neutralized with 2-(dimethylamino) ethanol to an amount equivalent to the methacrylic acid constituent of the polymer.

Step III Formulation of Coating Material A coating formulation is prepared from the following materials:

Materials Parts by Weight solution polymer from the Example Step II titanium dioxide 1 Water latex from this Example Step I 4 20% aqueous 2-(dimethylamine)ethanol "'defined in Example 25.

The coating material is formed from the above materials using the procedures of Step IV of Example 28. The resultant enamel adjusted to a viscosity of 20 seconds (Ford Cup No. 4) is sprayed on primed steel panels and baked for 25 minutes. The initial baking temperature is lC. This temperature is gradually raised to [80C and maintained at 180C for at least of the 25 minutes. The resultant coatings demonstrate good gloss and physical properties. The resistance of these coating-s to soaking in water at 32C for 240 hours is excellent.

EXAMPLE 36 A water-based enamel is produced in the following manner:

Step 1 Preparation of (let down) Latex 1. There is charged to a reactor 127 parts of water and 2 parts of stabilizer polymer prepared from the materials and using the procedures used to prepare the stabilizer polymer of Example 28.

2. The following reactant monomers and chain transfer agent are thoroughly mixed.

Materials Parts by Weight styrene 20.0 hydroxpyropylmethacrylate 14.0 methacrylic acid 6.0 butyl acrylate 25.0 butyl methacrylate 35.0 l-octanethiol 0.7

3. There is dissolved 0.5 parts of ammonium persulfate in 16.7 parts of water.

4. There is dissolved 0.1 parts of ammonium persulfate in 4.66 parts of water.

The latex is prepared from the above materials following the procedures of Step 11 of Example 28.

The resultant latex polymer, i.e., the emulsion polymer, has average molecular weight (M,.) of about 8,500 and a Tg of 20C.

Step [1 Formulation of Coating Material A coating material is prepared from the following materials:

The coating formulation is prepared from the above materials using the procedures of Step IV of Example 28.

EXAMPLE 37 The procedures of Example 28 are repeated with the difference that in preparing the soluble stabilizer poly mer of Step 1 there is used with the reactant monomers 3.5 parts by weight of l-octanethiol. The average molecular weight (ll 4,.) of the resultant stabilizer polymer is about 3,000. It has a Tg of about 8C.

EXAMPLE 38 The procedures of Example 28 are repeated with the difference that in preparing the soluble stabilizer polymer of Step 1 there is used with the reactant monomers 0.5 parts by weight of l-octanethiol. The average molecular weight (FL) of the resultant stabilizer polymer is about 10,000. It has a Tg of about 8C.

EXAMPLE 39 The procedures of Example 28 are repeated with the difference that in preparing the soluble stabilizer polymer of Step I the following reactant monomers and chain transfer agent are used:

Materials Parts by Weight mcthacrylic acid 15 methyl methacrylate 30 styrene 5 butyl acrylate 40 butyl methacrylate l0 l-octancthiol 2 The average molecular weight (M,,) of the resultant soluble stabilizer polymer is about 4,000. lts Tg is about 18C.

EXAMPLE 40 The procedures of Examples 1 and 28 are repeated with the single difference that in lieu of the commercially available amino resin (Cymel 300) crosslinking agent there is used a chemically equivalent amount of melamine resin prepared from the following materials and in the following manner:

Water (400 parts by weight), sodium hydroxide (3.5 parts by weight), and paraformaldehyde (326 parts by weight) are heated to reflux and refluxed 15 minutes. The solution is cooled to 85C, and the pH is adjusted to 8.5 with aqueous sodium hydroxide. Melamine (126 parts) is added, and the mixture is maintained at -90C for 10 minutes. Methanol (992 parts) and concentrated sulfuric acid (36 parts) are added and the mixture is stirred for about 1 hour. Upon addition of 320 parts 25 percent aqueous sodium hydroxide. a white precipitate is formed which is removed by filtration. Approximately 300 parts of a semi-solid methyl- 31 ated melamine are isolated from the filtrate by vacuum distillation and used in the formulation of water-based enamels.

EXAMPLE 41 The procedures of Examples l and 28 are repeated with the single difference that in lieu of the commercially available amino resin (Cymel 300) crosslinking agent there is used a chemically equivalent amount of a urea-formaldehyde resin prepared from the following materials and in the following manner:

Preparation of Urea-Formaldehyde Resin In a one liter three-necked flask equipped with reflux condenser, thermometer, and stirrer are placed 243 g. of 37 percent aqueous formaldehyde and 4-6 g. of concentrated ammonium hydroxide to bring the pH to 7.5-8.5. Sixty g. urea is added with stirring and the mixture heated to 100C over a 1 -hour period by means of a heating mantle. This temperature is maintained l and B hours. 64 g. methanol is added, followed by enough phosphoric acid to bring the pH to 5.5. The reaction is stirred for 1 hour. Water can be removed by heating 60-70C under a water aspirator pressure of IOU-200 mm. The resin can be dissolved in isopropyl alcohol to give a 60 percent solution. The term parts" when used herein without further designation shall mean parts by weight."

The term "acrylic monomer shall mean acrylic acid, methacrylic acid, esters of acrylic acid and a C C; monohydric alcohol, e.g., ethyl acrylate, butyl acrylate, hexyl acrylate and Z-ethylhexyl acrylate, esters of methacrylic acid and a C C monohydric alcohol, e.g., methyl methacrylate, butyl methacrylate, hexyl methylacrylate and 2-ethylhexyl methacrylate, hydroxyalkyl acrylates, e.g., hydroxyethyl acrylate and hydroxypropyl acrylate, hydroxyalkyl methacrylates, e.g., hydroxyethyl methacrylate and hydroxypropyl methacrylate. acrylamide, methacrylamide, methylolacrylamides, e.g., n-methylolacrylarnide. methylolmethacrylamides, e.g., N-methylolmethacrylamide, alkyl ethers of methylolacrylamides, e.g., N-isobutoxymethylolacrylamide, and alkyl ethers of methylolmethacrylamides, e.g., N-isobutoxymethylolmethacrylamide.

The term copolymer of acrylic monomers shall mean a polymer of at least two different monoethylenically unsaturated monomers of which more than 50 mole percent are acrylic monomers.

The term watendilutable organic solvent" means an organic solvent or mixture of organic solvents which is either miscible with water or will mix with water up to a concentration of at least one volume of-solvent per three volumes of water without phase separation. Ordinarily, such solvent, when present in the paint, enters the paint through its use in the preparation of the solution resin. as hereinbefore described. In such embodiment, the solution polymer is, of course, soluble therein. In another embodiment, it may be added independently, if desired. In the latter case. the solution polymer may not be fully soluble therein.

While there have been described herein what are at present considered preferred embodiments of the invention it will be obvious to those skilled in the art that modifications and changes may be made in the exemplary embodiments without departing from the essence of the invention. it is therefore to be understood that the exemplary embodiments are illustrative and not restrictive of the invention, the scope of which is defined in the appended claims. and all modifications that come within the meaning and range of equivalency of the claims are intended to be included therein.

What is claim is:

1. In an aqueous dispersion of paint in which a carboxy-functional polymer is at least partially neutralized with a water-soluble amine and dispersed with an amino resin crosslinking agent selected from melamine-formaldehyde resins and urea-formaldehyde resins in an aqueous solution of water and a water-soluble amine, the improvement wherein the film-forming components of said dispersion of paint exclusive of said amino resin comprises the combination of:

I. about 5 to about 50 parts by weight of a solution polymer which is a carboxy-functional copolymer of acrylic monomers that:

A. is at least partially neutralized with said watersoluble amine.

B. is soluble in said aqueous solution,

C. has average molecular weight (M in the range of about 3,000 to about 20,000 and D. has Tg in the range of l5C. to 50C., and

ll. about 50 to about 95 parts by weight of an emulsion polymer having functionality selected from carboxy functionality and hydroxy functionality and is a copolymer of acrylic monomers that:

A. is essentially insoluble in said aqueous solution,

B. has average molecular weight (m in the range of about 3,000 to about 20, 000, and

C. has Tg in the range of l5C. to 50C., and wherein said amino resin crosslinking agent is present in an amount in the range of about 15 to about 35 weight percent of the sum of the weights of said solution polymer and said emulsion polymer.

2. An aqueous dispersion of paint in accordance with claim 1 adapted for spray paint application by adjusting the water content thereof to between about 50 and about weight percent of said dispersion and adjusting the pH to between 7 and 10.

3. An aqueous dispersion of paint in accordance with claim 2 wherein about 5 to about 20 volume percent of the water in said dispersion is displaced by an equal volume of an essentially non-ionizable organic solvent for said solution resin.

4. An aqueous dispersion of paint in accordance with claim 3 wherein said organic solvent is an alcohol.

5. An aqueous dispersion of paint in accordance with claim I wherein in addition to said solution polymer and said emulsion polymer, said paint dispersion contains a stabilizer polymer which is a carboxy-functional acrylic copolymer that is soluble in said aqueous solution. has average molecular weight (371,) below that of said solution polymer and is present in said aqueous dispersion in an amount in the range of about 0.0l to about 10 parts by weight.

6. An aqueous dispersion of paint in accordance with claim 1 wherein in addition to said solution polymer and said emulsion polymer, said paint dispersion contains a stabilizer polymer which is a carboxy-functional copolymer of acrylic monomers that is soluble in said aqueous solution, has average molecular weight (V1,) in the range of about 3,000 to about 8,000, and is present in said aqueous dispersion in an amount in the range of about 0.025 to about 5 parts by weight.

7. In an aqueous dispersion of paint in which a carboxyfunctional polymer is at least partially neutralized with a water-soluble amine and dispersed with an amino resin crosslinking agent selected from mela- 33 mine-formaldehyde resins and urea-formaldehyde resins in an aqueous solution of water and a water-soluble amine, the improvement wherein the filmforming components of said dispersion of paint exclusive of said amino resin consist essentially of:

I. about to about 30 parts by weight of a solution polymer which is a carboxy-functional copolymer of acrylic monomers that:

A. is at least partially neutralized with said water soluble amine, B. is soluble in said aqueous solution, C. has average molecular weight (fi in the range of about 3,000 to about 20,000, and D. has Tg in the range of l5C. to 50C., ll. about 70 to about 90 parts by weight of an emulsion polymer having functionality selected from carboxy functionality and hydroxy functionality and is a copolymer of acrylic monomers that: A. is essentially insoluble in said aqueous solution, B. has average molecular weight (P3,) in the range of about 3,000 to about 20,000, and C. has Tg in the range of C., to 50C., and said amino resin crosslinking agent is present in an amount in the range of about l5 to about 35 weight percent of the sum of the weights of said solution polymer and said emulsion polymer.

8. An aqueous dispersion of paint in accordance with claim 7 having pH in the range of 7 to about 10.

9. An aqueous dispersion of the paint in accordance with claim 7 having pH in the range of 7 to about 9.5. 10. An aqueous dispersion of paint in accordance with claim 7 having pH in the range of 7 to about 9. 9. 11. An aqueous dispersion of paint in accordance with claim 7 wherein said solution polymer in addition to being carboxy-functional is also hydroxy-functional. 12. An aqueous dispersion of paint in accordance with claim 7 wherein said solution polymer in addition to being carboxy-functional is also amide-functional.

13. In a method for producing an aqueous dispersion of paint in which a carboxy-functional polymer is at least partially neutralized with a water-soluble amine and dispersed with an amino resin crosslinking agent selected from melaminet'ormaldehyde resins and ureaformaldehyde resins in a continuous phase consisting essentially of water-dilutable organic solvent and an aqueous solution of water and water-soluble amine, the improvement which comprises intimately dispersing with said water, said amine resin crosslinking agent and said water-soluble amine:

I. about 5 to about 50 parts by weight of a solution polymer which is a carboxy-functional copolymer of acrylic monomers that:

A. is at least partially neutralized with water-soluble amine,

B. is soluble in said aqueous solution,

C. has average molecular weight (T4,) in the range of about 3,000 to about 20,000, and

D. has Tg in the range of-l5C., to 50C., and

II. An aqueous emulsion consisting essentially of water, water-soluble amine, and about 50 to about parts by weight of an emulsion polymer having functionality selected from carboxy functionality -and hydroxy functionality and is a copolymer or acrylic monomers that: A. is essentially insoluble in said aqueous solution, B. has average molecular weight m in the range of about 3,000 to about 20,000, and C. has Tg in the range of l5C. to 50C., said amino resin crosslinking agent being present in an amount in the range of about 15 to about 35 weight percent of the sum of the weights of said solution polymer and said emulsion polymer and said water-dilutable organic solvent constituting between 5 and 20 percent of said continuous phase when the combination of said water and said water-dilutable organic solvent comprises 50 to 65 weight percent of said aqueous dispersion.

* I i i i 

1. IN AN AQUEOUS DISPERSION OF PAINT IN WHICH A CARBOXYFUNCTIONAL POLYMER IS AT LEAST PARTIALLY NEUTRALIZED WITH A WATER-SOLUBLE AMINE AND DISPERSED WITH AN AMINO RESIN CROSSLINKING AGENT SELECTED FROM MELAMINE-FORMALHYDE RESINS AND UREA-FORMALHYLDE RESINS IN AN AQUEOUS SOLUTION OF WATER AND A WATER-SOLUBLE AMINE, THE IMPROVEMENT WHEREIN THE FILM-FORMING COMPONENTS OF SAID DISPERSON PAINT EXCLUSIVE OF SAID AMINO RESIN COMPRISES THE COMBINATION OF:
 1. ABOUT 5 TO ABOUT 50 PARTS BY WEIGHT OF A SOLUTION POLYMER WHICH IS A CARBOXYL-FUNCTIONAL COPOLYMER OF ACRYLIC MONOMERS THAT, A. IS AT LEAST PARTIALLY NEUTRALIZED WITH SAID WATER-SOLUBLE AMINE, B. I SOLUBLE IN SAID AQUEOUS SOLUTION, C. HAS AN AVERAGE MOLECULAR WEIGHT (MN) IN THE RANGE OF ABOUT 3,000 TO ABOUT 20,000 AND D. HAS IN THE RANGE OF -15*C. TO 50*C., AND II. ABOUT 50 TO ABOUT 95 PARTS BY WEIGHT OF AN EMULSION POLYMER HAVING FUNCTIONALITY SELECTED FROM CARBOXY FUNCTIONALITY AND HYDROXY FUNCTIONALITY AND IS A COPOLYMER OF ACRYLIC MONOMERS THAT: A. IS ESSENTIALLY INSOLUBLE IN SAID AQUEOUS SOLUTION, B. HAS AVERAGE MOLECUALR WEIGHT (MN) IN THE RANGE OF ABOUT 3,000 TO ABOUT 20,000, AND C. HAS TG IN THE RANGE OF -15*C. TO 50*C., AND WHEREIN SAID AMINO RESIN CROSSLINKING AGENT IS PRESENT IN AN AMOUNT IN TH RANGE OF ABOUT 15 TO 35 WEIGHT PERCENT OF THE SUM OF THE WEIGHTS OF SAID SOLUTION POLYMER AND SAID EMULSION POLYMER.
 2. An aqueous dispersion of paint in accordance with claim 1 adapted for spray paint application by adjusting the water content thereof to between about 50 and about 65 weight percent of said dispersion and adjusting the pH to between 7 and
 10. 3. An aqueous dispersion of paint in accordance with claim 2 wherein about 5 to about 20 volume percent of the water in said diSpersion is displaced by an equal volume of an essentially non-ionizable organic solvent for said solution resin.
 4. An aqueous dispersion of paint in accordance with claim 3 wherein said organic solvent is an alcohol.
 5. An aqueous dispersion of paint in accordance with claim 1 wherein in addition to said solution polymer and said emulsion polymer, said paint dispersion contains a stabilizer polymer which is a carboxy-functional acrylic copolymer that is soluble in said aqueous solution, has average molecular weight (Mn) below that of said solution polymer and is present in said aqueous dispersion in an amount in the range of about 0.01 to about 10 parts by weight.
 6. An aqueous dispersion of paint in accordance with claim 1 wherein in addition to said solution polymer and said emulsion polymer, said paint dispersion contains a stabilizer polymer which is a carboxy-functional copolymer of acrylic monomers that is soluble in said aqueous solution, has average molecular weight (Mn) in the range of about 3,000 to about 8,000, and is present in said aqueous dispersion in an amount in the range of about 0.025 to about 5 parts by weight.
 7. In an aqueous dispersion of paint in which a carboxyfunctional polymer is at least partially neutralized with a water-soluble amine and dispersed with an amino resin crosslinking agent selected from melamine-formaldehyde resins and urea-formaldehyde resins in an aqueous solution of water and a water-soluble amine, the improvement wherein the filmforming components of said dispersion of paint exclusive of said amino resin consist essentially of: I. about 10 to about 30 parts by weight of a solution polymer which is a carboxy-functional copolymer of acrylic monomers that: A. is at least partially neutralized with said water soluble amine, B. is soluble in said aqueous solution, C. has average molecular weight (Mn) in the range of about 3, 000 to about 20,000, and D. has Tg in the range of -15*C. to 50*C., II. about 70 to about 90 parts by weight of an emulsion polymer having functionality selected from carboxy functionality and hydroxy functionality and is a copolymer of acrylic monomers that: A. is essentially insoluble in said aqueous solution, b. has average molecular weight (Mn) in the range of about 3, 000 to about 20,000, and C. has Tg in the range of -15*C., to 50*C., and said amino resin crosslinking agent is present in an amount in the range of about 15 to about 35 weight percent of the sum of the weights of said solution polymer and said emulsion polymer.
 8. An aqueous dispersion of paint in accordance with claim 7 having pH in the range of 7 to about
 10. 9. An aqueous dispersion of the paint in accordance with claim 7 having pH in the range of 7 to about 9.5.
 10. An aqueous dispersion of paint in accordance with claim 7 having pH in the range of 7 to about
 9. 9.
 11. An aqueous dispersion of paint in accordance with claim 7 wherein said solution polymer in addition to being carboxy-functional is also hydroxy-functional.
 12. An aqueous dispersion of paint in accordance with claim 7 wherein said solution polymer in addition to being carboxy-functional is also amide-functional.
 13. In a method for producing an aqueous dispersion of paint in which a carboxy-functional polymer is at least partially neutralized with a water-soluble amine and dispersed with an amino resin crosslinking agent selected from melamineformaldehyde resins and urea-formaldehyde resins in a continuous phase consisting essentially of water-dilutable organic solvent and an aqueous solution of water and water-soluble amine, the improvement which comprises intimately dispersing with said water, said amine resin crosslinking agent and said water-soluble amine: I. about 5 to about 50 parts by weight of a solution polymer which is a carboxy-functional copolymer of acrylic monomers that: A. is at least partially neutralized with water-soluble amine, B. is soluble in said aqueous solution, C. has average molecular weight (Mn) in the range of about 3, 000 to about 20,000, and D. has Tg in the range of -15*C., to 50*C., and II. An aqueous emulsion consisting essentially of water, water-soluble amine, and about 50 to about 95 parts by weight of an emulsion polymer having functionality selected from carboxy functionality and hydroxy functionality and is a copolymer or acrylic monomers that: A. is essentially insoluble in said aqueous solution, B. has average molecular weight (Mn) in the range of about 3, 000 to about 20,000, and C. has Tg in the range of -15*C. to 50*C., said amino resin crosslinking agent being present in an amount in the range of about 15 to about 35 weight percent of the sum of the weights of said solution polymer and said emulsion polymer and said water-dilutable organic solvent constituting between 5 and 20 percent of said continuous phase when the combination of said water and said water-dilutable organic solvent comprises 50 to 65 weight percent of said aqueous dispersion. 